Electrostatic air filter and circulator



Dec. 7, 1948.

s. w. CRISE 2,455,738 ELECTROSTATIC AIR FILTER AND CIRCULATOR Filed June so, 1945 3mm George W Crzlse Patented Dec. 7, 1948 ELECTROSTATIC AIR FILTER AND .QIRCULATOR George W. Crise, Coliunbus,Ohio

Application June so, 1945. Serial No. 602,551

F The presentinvention relates to air filters jand circulatorsof the electrostatic type wherein precipitation of. dustand other foreign particles is produced by} subjecting the air to alternatepotentials of e1ectros.tatic fields. i t a It has ibeen wellestablished that when air containing dustis subjected to a strong electricjpotential of constantpolarity such as accrues when air is circulated in close proximity to highly charged; electrodes; dust particles therein become electrostatioally. charged so that they are subject ftojstrong attraction by any oppositely charged jelectrode which 3 they approach or contact? In tthe past many successful units have been builtlembodying this principle, but thesize, cost and current required for their operationhas limited their practicalfield. of application. Therefore; the objeot o f my invention is. to produce enhancer ofthis type of such simple and inexpensive: construction as to makeit more readily availableto the general public.

Another "object is to providaan air filter so constructed as to eliminate the need for electronic v acuum tubes, with their limited life and replacement costs, thus providinga unit requiring no replaceable parts during aiprolonged period of normal use, 7 e e e t i 1 Another object is .to provide an electrostatic air filter so constructed as to reduce current can.- sumptiori to a small fraction of that heretofore required in filters of this general nature.

Another object is to provide a filter unit which 8 Claims. (01. 183- 7) 2 H 31 through the commutator of the fan on the plane indicated by the line 4 -4 of Fig.

Referring to the drawings, the motor, indicated at 5, advantageously may be of the B-pole synchronous type; designed to operate at U 990 R. P. M. on standard 60 cycle current. The armaturefi of the motoris madevpreferably of lamie nated silicon-transformer steel and provided with poles I which correspond in spacing 'with the pole projections 8 formed on the stator 9, so that when started, the motor runs at asynchronous speed. The statorQS has, in addition to a normal willtweighbut a few pounds so as to make it readily portableand capable of being carried from room to room forthe convenience of those suffaring from. such ailments as hay fever. Broadly, theprinciple of my invention resides in combining the functions of afan motor, transformer;rectifier, electrodes and cabinet into a single compact andportable unit. For this purpose,- I employ .a synchronous motor carrying a synchronous commutator, said motor having on itsstator high voltage windings for electrostatically energizing lan air-circulating fan, the lat terserving as a primary electrode and for forcing the air as charged througha fan guard of oppositeipolaritys u i a a "H connection with the above, I have also worltecl out certain novel details of construction and arrangements of parts, all of which aremore fully de eloped. in the ,following description and illustrated in the accompanying'drawlng, wherein: l l

oFig 1 is a side elevational view of an electroand fan formed in accordance stat c; air filteri witnthe prefient invention; 1; t t

. Fig. .2 is a front elevational view thereof; Fig. 3 is a diagrammatic view of thefan motor audits armature; .1 l 1 Ffig 4 is a detail vertlcalnsectional View taken primary winding IU -a pair of high voltage wind ings I I, the latter being formed with high voltage terminals [2 which .endiin a; group of. sharp points, indicated at [3. e

By referringto Figs. 1 and 3} it will be noted that these barbed or sharp pointed electrode terminals are mounted on a fixed insulating support 14, the electrodes having spacings of approx imately degrees so asto register with the commutator segments shown atl ij and I5.,, Each commutator bar is equipped with barbed or sharp pointed electrodes l6 Which are positioned to regr ister in close point to pointrelation with the electrode ends [3 as thecommutatorrevolves. The commutator bars are alternatelygrounded. and connected to thehub of the fan ll andthemotor shaft 1| 8, The fan guardshown at l9 .may be easily removed from its frame carried supports 2I1 for convenience in the cleaningthereof. The fan blades, if desired, may be provided with barbed points shown at 2| forthepurpose ofina creasing electrostatic radiation when necessary.

The operation of my improved fan and filter may be summarized as follows: The motor primary'winding l 0 is energized with a standard a1- ternatingcurrent. A cable, not shown, is passed through the opening 22 provided in one end of the motor shaft l8, and givena few wraps around the shaft, the cable being then pulled, bringing M. while it continuesto the ran up to .900. RQP. run bytthe lwell known L electric engine. principle, inthe same manner; as is commonly used on many phonograph turntables. Thecommutator, which has the same number. of segments as the armature; hastpoles; and rotating with the;

same shaft, brings alternate setsof segments into registration with a terminals l3; 7

Current jumps from the terminals I 3 to the barbed segments I5 and I5, by what is ordinarily known as. brush discharga as scenes the motor reaches its normal rotating speed, so that the fan andframe each change positions electrically as the current inthe stator coils alternates; the

barbedpoints of thebrush terminals 13 and the electrodes Since the. fan as a polarizer. commutes only the amountof currentlost byradlati'omto the dust pair of high voltage barbed- 1'6 passing on thepeakof each'cycle.

3 particles, practically no current flows between the terminal points after the motor has started. For example, if the motondrops into synchronism with itsfipolaritypo'sitive, it will remainpositive as long as it runs, and the motor and frame and connected guard will stay negative from the same source. If the fan frame is actually grounded, as by using an indicating plug, no potehti alwill oc cur between the fan guard and the user. However, if no external ground is used, onlya light static spark of negligible current can be felt by the user if the fan should be' tou'cl'ied while in operation. The actual power potential exists between the fan and the @guard, but this is not of a dangerous value due to the resistance of the windings which are required to supply only a fraction of one mil'liazripeije.

Afterth'e air'paSSe's'th'rQUgh the fan n, and is charged thereby, the dust/particles are collected byahd settle on the guard I 9, which can be conveniently 'rem'oved for periodical cleaning. It ivill be"understocdthat astandardfsquirrel cage type 'oi's'ynchronous motor 'maybe used in place of 'the type shown, in :which case the fan is self starting "if 'conventioria1 windings are used. Such astan'd-ar'd motor, however, uses more "current -and"isnior'eeiipensiveto build, but does not require any changes in the operating principles of my invention.

ning, and the high voltage coils H are energized, that since thefnuniber ofcommutator segments is the same as thenuiilb'er of armature pole pieces, both pole pieces and commutator'segments move one position with each reversal of the field current, thecom'mutator'ends l5 and I5 remaining at fixed andopposite polarity by the well known principle of commutation.

since thewo'mmutator ends l5 are electrically connected to the .motorshaft, frame and front s'cr'eenby metallic contact, and since the fan ll, having-the barbs 21, is connected to the opposite commutator en'ds l5, then the fan and. guard screen must 'be at co'rresponding opposite potentials as long as th'eian is in operation.

} Inasmuch as the fan carries the electric-ally charged barbs 2! through the air at high speed, and since the fan sets relatively'clos'e to the 'fan guard screen which is "of opposite polarity, a

corona discha'rge will takefplace between the barb p'oir its lll' and the screen I9, and'suchcorona will be in relatively close proximity to all dust particleswhich are in 'the'air and through which the barbs 21 are driven,

Zistlieair flow's forward through the fan guard screen I 9, "all charged dust particles will be cartied i-nto close proximity with oppositely charged wireof wlii-ch'the mesh is constructed, and while ithasbee'n customary touse relatively large diameter connecting rods'to prevent the tendency of corona formation on the collector electrodes, the comparatively large mesh "screen illustrated *provides the advantage or forcing all air tofiow relatively-close to the "collector, -so that dust particles need move only slightly from their neutral path to reach the surface "of opposite potential.

1.- An electrostatic airfilter and "fan comprising: a synchronousalternating current motor includingia stat'or having a name, an armature, an armature shaft, 'a primary low-voltagewin'ding on the stator, 'a secondary high-voltage winding disposed on the stator in inductive relationship to-the slow-voltage windingand a current recticommutatoriflxedto 'rotatewith the armatwill be noted that "when the motor is 'runture shaft, a bladed fan rotatable with said commutator, a metallic fan guard carried by the stator frame, the periphery of said. commutator being formed with electrically spaced bars carrying radially extending electrodes, alternate bars of said commutator being electrically joined with said armature shaft and said fan, and spaced sets of stationary electrodes joined with the secondary winding and insulated from said stator frame, said stationary electrodes being disposed in close physical relation to but Without actual cont-act with the'electrodes of said commutator bars.

2. An electrostatic air filter and fan structure comprising: a synchronous alternating current motor "embodying -a stator having a frame, an armature, an armature shaft, a primary lowvoltage winding for the stator, a secondary high-- voltage winding disposed on the stator ini'n'ductive relationship tothe low-voltage winding, and a curr'ent-rectifying commutator fixed to rotate with the armature shaft, a bladed fan rotatable with said commutator, a metallic fan 'guard'c'ar ried by said stator and electrically energized by its field, said armature being formed with"*p'olt=is, pole projections on the stator in registration with the poles of the armature, the periphery of said commutator being formedwith electrically spaced bars carrying'radia'lly extending electrodes, alternate bars of said coinmutator bein'g' 'electricall'y joined with said armature "shaft and said fan, and spaced sets of s'tationary'electrodes joined with the terminals of thes'econd'ary winding, said stationary electrodes "being insulated from said stator frame andarranged in close physical relation but out of actual contact with the electrodes of sa'idcommutator bars.

3. An electrostatic air filter and fan'construction as specified in claim 2, "and wherein the blades of the fan are provided with a"multiplicity of "electrodic projections. i

4. An electrostatic air filter and fan construction as defined in claim 2, andwherein means are provided for removably mounting the fan guard in connection with the stator frame.

5. In combination with a synchronous motor having a stator and a motor winding, a high-voltage winding on the stator, a bladed air-moving fan driven by said motor, and a commutat'or'for rectifying the current obtained from said winding and applying the same to 'said fan.

6. In combination with a synchronous motor having a stator and "a motor winding, a high"- voltage winding on the stator, a bladed air-moving fan driven by said motor, a 'commutato'r for rectifying the current obtained from said winding and applying the same to said fan, and a fan guard positioned in front of said fan and connectedwith said stator, said fan guar'd possessing a polarity-during opera-tion of said motor opposite to that of 'the 'fan blade.

7. In a device for cleaning airby electrostatic precipitation, a charging electrode, a precipitating electrode, and means for maintaining said electrodes at opposite polarity, said means including a rectifying commutator, a motor driving said commutator, 's'aidmotor including a stator and a winding for imparting motive energy to the motor, a second winding wound on the stator of saidv motor for gathering high voltage from the motor winding, and conductors for leading power from thesecond winding to the commutator.

8. An electrostatic air filter and fan- "structure comprising: a synchrbnous alternating current motor embodying a stator having a frame, an

armature, an armature shaft, a primary lowvoltage winding for the stator, a secondary highvoltage winding disposed on the stator in inductive relationship to the low-voltage winding, and a current-rectifying commutator fixed to rotate with the armature shaft, a bladed fan rotatable with said commutator, a metallic fan guard carried by said stator and electrically energized by its field, said armature being formed with poles, pole projections on the stator in registration with the poles of the armature, the periphery of said commutator being formed with electrically spaced bars carrying radially extending electrodes, alternate bars of said commutator being electrically joined with said armature shaft and said fan, and spaced sets of stationary electrodes joined with the terminals of the secondary winding, said stationary electrodes being insulated from said stator frame and arranged in close physical relation with the electrodes of said commutator bars.

GEORGE W. CRISE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 895,729 Cottrel Aug. 11, 1908 1,343,285 Schmidt June 15, 1920 1,377,205 Krause May 10, 1921 2,129,785 Penney 1 Sept. 13, 1938 2,297,933 Yonkers Oct. 6, 1942 FOREIGN PATENTS Number Country Date 287,649 German Sept. 30, 1915 

